(1) Field of the Invention
The invention relates to a method for removal of residues after pattern etching in the fabrication of integrated circuits which employs an organic solvent which is more effective in the removal of the polymerized residue left after plasma-enhanced etching of polycrystalline silicon layers, or polysilicon, and is not potentially deleterious to the rest of the integrated circuit.
(2) Description of the Prior Art
The etching of layers of polysilicon into patterns useful in the manufacture of semiconductor integrated circuits is done by plasma-enhanced reactive gases such as chlorine, hydrogen bromide, and sulfur hexafluoride. Such subtractive etching reactions leave behind a residue after etching is complete and the photoresist etching mask is removed by ashing in oxygen plasma. This residue is found on the sidewall of the trench etched in the polysilicon and must be removed. The residue consists of a complex polymer formed from photoresist, the reactive gases, and their reaction products. It is commonly removed by using ammonia and hydrofluoric acid solutions, but this process must be carefully controlled to prevent these reagents from attacking portions of the integrated circuit such as the gate oxide insulation and tungsten metallization, for example. U.S. Pat. No. 5,296,093 to Szwejkowski shows the conventional use of ammonia and hydrofluoric acid solutions for residue removal after etching. Organic solvents have not been considered for this purpose due to concern over the introduction of contaminants. The use of organic solvents for stripping photoresist has been discussed in "A Proven Submicron Photoresist Stripper Solution for Post Metal and Via Hole Processes" by Wai Mun Lee, EKC Technology, Inc. 2520. Barrington Ct. Hayward, Calif. pp. 1-6, but not in combination with ashing removal of photoresist or the presence of polymeric residues or their removal.